use anyhow;
use derive_builder::Builder;
use getopts::Options;
use pdf_forms::{Form, FieldType};
use serde::{Deserialize, Serialize};

use std::env;
use std::fs::{File, OpenOptions};
use std::io::{Read, Write};
use std::path::Path;
use std::process;

#[derive(Debug, Default, Deserialize, Serialize)]
struct TextForm<'a> {
    #[serde(borrow)]
    fields: Vec<Field<'a>>,
}

#[derive(Debug, Builder, Deserialize, Serialize)]
struct Field<'a> {
    id: usize,

    #[builder(default)]
    value: Option<&'a str>,

    #[builder(default)]
    state: Option<bool>,
}

fn print_usage(opts: &Options) {
    print!(
        "{}",
        opts.usage("usage: formurapid [options] (--generate | --fill) PDF_FILE"),
    );
}

fn main() {
    match run() {
        Ok(_) => (),
        Err(e) => {
            eprintln!("error: {}", e);

            process::exit(exitcode::SOFTWARE);
        },
    }
}

fn run() -> anyhow::Result<()> {
    let args: Vec<String> = env::args().collect();

    let mut opts = Options::new();
    opts.optflag("", "fill", "fill in the form using a markup file");
    opts.optflag("", "generate", "generate helper files to fill in the form");

    let opt_matches = opts.parse(&args[1..])?;

    if opt_matches.free.is_empty() {
        print_usage(&opts);

        process::exit(exitcode::USAGE);
    }

    let form_path = Path::new(&opt_matches.free[0]);
    let form_file_prefix = form_path
        .file_stem()
        .ok_or(anyhow::anyhow!("no file name"))?
        .to_str()
        .ok_or(anyhow::anyhow!("error converting file name"))?;

    let toml_file_name = format!("{}.toml", form_file_prefix);
    let toml_path = form_path.with_file_name(toml_file_name);
    let output_file_name = format!("{}-filled.pdf", form_file_prefix);

    let mut form = Form::load(form_path)?;

    if opt_matches.opt_present("fill") {
        return fill(
            toml_path,
            form_path.with_file_name(output_file_name),
            &mut form,
        );
    } else if opt_matches.opt_present("generate") {
        let ids_path = form_path.with_file_name(
            format!("{}-ids.pdf", form_file_prefix)
        );

        return generate_fill_helpers(
            toml_path,
            ids_path,
            &mut form,
        );
    } else {
        print_usage(&opts);

        process::exit(exitcode::USAGE);
    }
}

/// Generate files to fill in the form.
///
/// Generates a TOML file at `data_path`, and a PDF with IDs entered in the
/// form's text fields in `output_path`.
fn generate_fill_helpers<P: AsRef<Path>>(
    data_path: P,
    output_path: P,
    form: &mut Form,
) -> anyhow::Result<()> {
    let mut data = TextForm::default();

    for i in 0..form.len() {
        let field_type = form.get_type(i);

        match field_type {
            FieldType::Text => {
                form.set_text(i, format!("{}", i))?;

                data.fields.push(
                    FieldBuilder::default()
                        .id(i)
                        .value(Some(""))
                        .build()?
                );
            },
            FieldType::CheckBox => {
                data.fields.push(
                    FieldBuilder::default()
                        .id(i)
                        .state(Some(false))
                        .build()?
                );
            },
            _ => (),
        }
    }

    let mut toml_file = OpenOptions::new()
        .create_new(true)
        .write(true)
        .open(data_path)?;
    toml_file.write_all(&toml::to_vec(&data)?)?;

    form.save(output_path)?;

    Ok(())
}

/// Fill in `form` with values from `data_path` and write to `output_path`.
fn fill<P: AsRef<Path>>(
    data_path: P,
    output_path: P,
    form: &mut Form,
) -> anyhow::Result<()> {
    let mut buf = Vec::new();
    let mut file = File::open(data_path)?;
    file.read_to_end(&mut buf)?;

    let data: TextForm = toml::from_slice(&buf)?;

    for field in data.fields {
        if let Some(value) = field.value {
            form.set_text(field.id, value.to_owned())?;
        } else if let Some(state) = field.state {
            form.set_check_box(field.id, state)?;
        }
    }

    form.save(output_path)?;

    Ok(())
}